Enable configuration of evaluation periods in lambda alarms

With cdk-watchful, you can easily create cloudwatch alarms to monitor lambda through the watchLambdaFunction class.
However, it is not possible to fine-tune alarm conditions because the evaluationPeriods for triggering alarms cannot be set to anything other than the default value of 3.

Therefore, we would like to pass evaluationPeriods from the argument to make it configurable.